Torque responsive device



GENERHTOB flux May 30, 1950 G. E. FROST TORQUE RESPONSIVE DEVICE Filed Nov. 9, 1944 Game/woe mmf Che: mmJ.

Giaeq: E fie.-

INVENTOR.

ATTORNEY Patented May 30, 1950 STATES- PAT EN OFFICE TORQUE RESPONSIVE DEVICE George Frost, Arlington, Va.

Application November 9, 1944, SerialgNo; 562,638.:

13 Claims. (01. B -134i (Granted under the act of March, 3, 1883, .as;

amended April 30," 1928; 370 O. G. 757) 2 Many elec'trid generators aredriven by. prime; In describing in detail my-novel torque respon movers; having ,a substantiallyconstant. torque sive device; which is considered tob'e-an improve characteristic,th'roughoutitheinnormal rangeiof; ment over the device shownin- U1 S;- Patent Now operating speeds TypicaLof, such. prime-mov- 1,795,905 issued March:10,1931, reference will be: ers' are the gasolineVengine Diesel.engine, and 51 made to the attached, drawings, In the drawcertain types roffelectrimmotorst With these ings: prime 'movers adevic'e ,resppnsiyeto. torque can Figure 1 isa view of a torque responsive device perform a varietyptusefulfunctionsincluding; constructed in accordance withthe principes of controloffuelinputto tli'elprime mover, providethe present invention andappliedto indicate the ingjan' indicationgoi trloque forthe benefit. of the Y torque of a shunt wound directr n n r r. operator, decreasingthe generator load .when al- Figure 2 is a g ry View like F ure 1 but lcwable. torqueeis exceeded, and many others, wi h torque responsive v ppl d o Mechanical Ltorque responsive devices arenot indicate the qu of aishunt-woul'ld direct C suitable for installation in most generating plants i e t generator a substantial armature because theyare cumbersome, expensive and inactionaccurate.,, Furthermore, they donot provide an. Figure 3 is ELI-fragmentary Viewv ke Figure 1' electric indic'atiiin cfitorque s'uitable fortoperation t s w g the torque responsive d v e appl ed. of"electricwrelaysn. Mechanical torque measuring to indicate the torque of a cumulative compound devices. valsd .haveconsiderable inertiaeand fail to Wmlnddirect current e e tOrrespond accurately, to, rapid ,changes cottorquea 205 Figure 4 is a hs yw w e u e 1* It isthereiore,highlydesirable. to.-,have a torque but showing application of torque responsive responsive device, entirely, electric in operationdevice to a ys po d Wound direct. and actuated by electrical conditions on thegen- Current generatoreratorirathenthan, mechanicaliconditionsin the Figures 5a and are Charts illustratingthev prime mo er. 5 correlation between the effective saturation curve An electrical torque measuring device is useful of the generator o which the torque responsive i i connection t other dynam0-e1e tyic l device of the present invention; is applied and the i hi as 11 generators For instance it effective saturationcurve of. thecoreportion. of. may be used on motors to determine load torque. the torque p ns ve device-i requirements Aspthetempemture rise .of a Figurefiis a fragmentary. viewv of theicore oi? namo-e1ect j m c is approximately propthe torque responsive device of the present inL tional tothetorque ,itiis developing .or'absorbing, vention and illustrating one method of adopting a torque measuring device maybe used t jndb it for use with aidirectcurrentmachine-.having catethe relative .valueofsarmatureheatings 3 effectiveisatumtion curve departing S It is therefore a general object ofithis-invenr from tioni,toprovide.meansndirectly "responsive to the AS shown'in Figure the torque responsive fi torque-of. a. primevmoverhdrivingr-an electriczgenindicated-1 generally at comprises a t netic core portion l defining amagnetic-flux patl'r 11-, isals o annbiect of this inventjomto provide separate from thedirecticurrent machine indicattorque,l'espgngive devjce suitableffopuse-hin. n 40 ed generally at G, Arotor; 3 sustainsthe coill tYQGSwOf,idyinamo-elggtfic.machinery of thedirect IILIJOSltlOn tohnkthe magnetic flux enclrchng currentgtypzeh thefiux path defined by core I. Aspring 4' is- A further object ofrthisainvention is-to accomprovided to oppose rotations of'thelotorl plishthe desired result-electrically and'inaman- Ibis well known that the torque of a direct n n r adil ,ad ptabl i fo useionrehctrminstru-r current machineis proportional tothe product ofmenlts, orwreladysn flux in the magneticfield and current in the ar-- A- further object :ofethis invention is :to provide mature conductorsa device accurately: indicating the prime mover torque irrespective rofithe; effectspf magnetic sat- (1) uration-s armature reaction; andnthe various field windings "on (the. fmachineif where it and is. arethe machine flux and armature Finally, itis :anxobjectof myinvention to secure current respectively.

these-results irra simple;and-sconvenient manner Similarly, if movable coil 2 be mounted in the using equipment having a high degree of re1i-' magnetic field-m, asshown in Fig. 1, torquewill abilityr be exerted on the coil! of a'mag-nitude propor-' tional to the field flux, (15m, and the current, im, passing through the coil.

By placing restraining spring 4 on the rotor 3, counter torque proportional to the deflection of the coil is produced. Since the coil will come to rest where the torque due to the flux and current equals the counter torque of the spring, the deflection, D, of the coil will be proportional to the product of field flux and coil current.

if the flux, 45m, in the core is made proportional to the flux in the machine and the current, im, in the movable coil is made proportional to machine armature current, deflection will be proportional to the products of these two qualities.

But, from Equation 1, the product of machine flux and armature current is equal to the torque on the machine. Hence:

The deflection of the coil is therefore proportional to the machine torque.

The above relations are true provided magnetizing effects and rotation of coil 2, Fig. 1, do not influence the flux passing through it. I avoid magnetizing difficulties by using a relatively weak spring, 4, a light rotatable structure, and a large air gap so that the ampere turns required to achieve the meter torque for maximum displacement are small compared with the ampere turns in the remainder of the magnetic path. The magnetomotive force produced by the coil is thereby made negligible with respect to the magnetomotive force in the core. To avoid change in flux linking the meter coil due to its own rotation I make the coil 2 of such size that it can turn through the maximum desired angle without altering the flux linked by the coil.

The construction of core, I. may be of any of the types well known in the art, for instance, the cross-section may be round, square, rectangular, or any other shape as most convenient in any particular design. The core should preferably be of laminated steel but other core materials such as cast iron will work satisfactorily. Rotor 3 is also preferably made up of a stack of steel laminations.

In the view of Figure 1, the torque responsive device of the present invention is shown as applied to indicate the counter-torque of a shunt wound D.-C. generator. For this purpose the rotor 3 is provided with a pointer I8 which cooperates with the scale I! to indicate the degree of rotation of the rotor.

In order to establish a magnetic flux m in the core I in accord with the fiux effective in generating voltage in the armature 5 of generator G, a winding I2 is placed on the core I as indicated. The terminals of this winding are connected to the shunt resistance It! which carries the current flow in the shunt field winding I of the generator G and hence develops a voltage across winding I2 in accord with the shunt field current of the machine.

Current flow in shunt field winding I is derived from source 8 through the circuit which may be traced through source 8, shunt resistance It, shunt field winding I, and adjustable resistance 9.

The winding 2 of the rotor 3 is connected to the shunt resistance II which carries the armature current of the generator G. Thus current is caused to flow in the winding 2 in accord with the armature current of generator G.

Since the current flow through winding I2 sets up flux m in the core I in accord with the flux of the generator G and the current in coil 2 links that flux and is in accord with the armature current flow of generator G, the torque exerted on rotor 3 varies in accordance with the torque of the generator G. The spring 4 is accordingly defiected in accord with the generator torque and that torque may be read on an appropriate scale In the drawing at Figure l, the generator G is as driven by a Diesel engine I5.

Figure 2 shows the torque responsive device of the present invention adapted to measure the torque of a D.-C. generator having substantial armature reaction. This mechanism differs from that of Figure 1 in that the additional winding I4 is provided on core I and is connected through adjustable resistance l3 to the shunt resistance II. Since the voltage drop across the latter resistor varies in accord with armature current of generator G, the current flow through winding I4 varies in accord with armature current.

Since the armature reaction, or demagnetizing efiect of armature current, acts in opposition to the field current flow in creating fiux in generator G, the winding 14 is wound to oppose the winding I2 in setting up flux m in the core I. This effect is indicated in Figure 2 of the drawing by the opposed arrows 2 and 2| showing the directions of magnetomotive force of the coils l2 and I 4, respectively.

In the mechanism of Figure 2, the adjustable resistance I3 is varied to the value at which the relative contributions of windings I2 and I 4 to the flux sm are in accord with the relative contributions of the field current flowing through field winding 1 of the generator G and the armature current flowing through the armature winding 5 thereof to the magnetomotive force of the generator.

Expressed mathematically, resistance I3 is adjusted until:

where:

m. m. f.12 is the magnetomotive force due to current in coil I2.

m. m. fr is the magnetomotive force due to generator shunt field current.

m. m. 14 is the magnetomotive force due to current in coil I4.

m. m. f.a is the direct axis component of magnetomotive force due to armature current flowing in the armature.

Figure 3 shows the application of the torque responsive device of the present invention to a generator G having a cumulative compound field winding 6. The cumulative compound winding connection is indicated by the arrows 22 and 23 representing the magnetomotive forces due to current fiow in the shunt and series field windings respectively and which have like orientations on the drawing. The connections in this case are like those of Figure 2 but coil I4 is wound in the opposite direction to produce magnetomotive force in aiding relationship with that of winding I2 as indicated by the like orientations of arrows 20 and 2| representing the directions of the magnetomotive forces of windings l2 and I4 respectively.

In the mechanism of Figure 3, the resistance m. f. m. m. f. m. m. f. m. m f...

I3 is adjusted until the magnetomotive forces produced in core I by the windings I2 and M are in accord with the relative contributions of the shunt field current and armature current respectively, to the total magnetomotive force of the machine. then proportional to the flux in generator G and the torque produced by current flow in that coil is proportional to the generator torque.

Figure 4 shows the torque responsive device of the present invention as applied to a difierential compound wound D.-C. generator. The connections in this case are like those of Figure 2 in order that current fiow through the winding I4 shall decrease the flux m in core I in the same manner that armature current fiow in the differential field winding decreases the generator flux. These opposing magnetomotive forces in the machine and in the torque responsive device are indicated by the opposed arrows 22 and 23 and 20 and 2|, respectively.

In the structure of Figure 4, the resistance I3 is adjusted until the magnetomotive forces of windings l2 and H are in accord with the relative contributions of shunt field current flow and armature current flow to the total magnetomotive force of the generator G.

I The foregoing description is based on the premise that successive increments of magnetomotive force on core I produce variations of fiux 5111 in accord with the contributions of the corresponding successive increments of field magnetomotive force in the machine to the machine flux. In other words, the core I defines a magnetic flux path having an effective saturation curve substantially like that of the generator G. Figures 5a and 5b show a pair of characteristics of this type for the specific case of a generator having an efiective saturation curve departing to a substantial degree from a straight line characteristic in the upper range of total field magnetomotive force. As indicated, the core I is designed to have a similar degree of departure from a straight line characteristic in the range of magnetomotive force values corresponding to this range of total field magnetomotive force. If the generator has a greater or lesser degree of departure from a straight line characteristic in the range of operation, or follows a straight line characteristic, the effective saturation curve of the core I is chosen accordingly to give an efiective saturation curve like that of the machine.

If the efiective saturation curve of the generator departs from a straight line to a substantial degree as, for example, as is shown in Figure 5a, the cross section and material of core I may be chosen to achieve the characteristic required. Alternatively, the core may be provided with a narrow saturating portion I9, Figure 6, to saturate and provide the necessary departure from a straight line characteristic.

Other forms of my torque responsive device for use in machines of different types will be evident to one skilled in the electrical art. For instance, if the machine has an additional control field producing magnetomotive force in the direct axis, it would be apparent that the object and spirit of my invention can be carried out by providing a suitable additional coil on core I.

In the specification, I have used the term "direct axis to denote that path of the generator wherein fiux generates voltage in the armature. I use this term to distinguish the cross-axis or quadrature axis wherein flux may exist and produce no voltage in the armature.

The flux in core I linked by the coil 2 is The term "dynamo-electric machine as used herein is intended to cover all types of direct current machinery having a current carrying armature and a field structure.

' I do not propose that my invention be limited to any one application of my torque responsive device, but instead broadly claim it for use as a torque indicator or meter, relay, or any other form apparent to one skilled in the art. I also claim its use in the measurement of torque on electric motors as well as generators.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. A mechanism to measure the torque of a direct current machine of the type having an armature and a field winding, said mechanism including a core defining a magnetic fiux path separate from said machine; said core having an efiective saturation curve substantially like that of said machine; a winding encircling said fiux path; means to produce electromotive force across said last winding in accord with the current flow in said field winding; a movable coil disposed to be linked with the flux in said core; yielding means restraining motion of said coil; and means for causing current flow in said coil in accord with the armature current of said machine, the magnetomotive force of said coil being negligible as compared with the magnetomotive force of said last winding.

2. A mechanism to measure the torque of a direct current machine of the type having an armature and a plurality of field windings, said mechanism including a core defining a magnetic flux path separate from said machine and having an efiective saturation curve substantially like that of said machine; windings about said core corresponding to said field windings; means to produce electromotive force across each of said last windings in accord with the current fiow in the corresponding field winding, said means being proportioned to cause each of said last windings to produce magnetomotive force in said core in accord with the relative contribution of the corresponding winding to the magnetomotive force of said machine, thereby to produce flux in said core in accord with the flux intercepted by the armature winding of said machine; a movable coil disposed to be linked by the flux of said core; yielding means restraining motion of said coil; and

vmeans for causing current flow through said coil in accord with the armature current of said machine.

3. A mechanism to measure the torque of a direct current machine of the type having an armature and two field windings, said mechanism including a core defining a magnetic flux path sep-- arate from said machine and having an effective saturation curve substantially like that of said machine; a pair of windings about, said core; means to produce electromotive force across each of said windings in accord with the current flow in the corresponding field winding, said means being proportioned to cause each of said last windings to produce magnetomotive force in said core in accord with the relative contribution of the corresponding winding to the magnetomotive force of said machine, thereby to produce flux in said core in accord with the flux of said machine; amovable coil disposed to be linked with the flux or said core; yielding means restraining motion of aao'aaaz 7 u said ,coil; and'means. for causing current; flow through: said: coiliin accord with the armature current ofsaid machine.

4. A mechanism to measure the torqueof a direct current machine of the type having an armature and a field winding and in which the armae ture exertssubstantialmagnetomotive force during normal operatiomsaid mechanism including, a' core defining a magnetic flux path separate.

fromsaid machine and having an effective saturation curve substantially like that of said machine; a pair of windings aboutsaid core; means lJO'IJIOdllCG electromotive force across one of said windings in. accord with the armature current of said machine and across the other of said windings in accord with the current in the field winding of said machine, said means being. proportioned to cause the relative magnetomotive forces of said windings to be in accord with the relative contributions of the field winding of said machine and the armature of said machine'to the magnetomotive thereof, thereby to produce flux in said core in accord with the flux of said machine; a movable coil disposedto be linked with the flux of said core; yielding means restraining motion of said coil; and means for causing current flow through said coil in accord with the armature current of said machine.

5. A mechanism to measure the torque of a direct current'machine of the type having'an armature, a shunt field winding, and acumulative compound field winding, said mechanism including a core defining a magnetic flux path separate from said machine and'having anefiective saturation curve substantially like that of said machine; a pair of windings about said'core; means to produce electromotive force across one of said windings in accord with the armature current of said machine and across the other of saidwindings in accord with thecurrent in the'shunt field winding of said machine, said means being'pro portioned to cause the relative magnetomotive forces of said windings to act cumulatively and in accord with the relative contributionsof shunt field current flow and armature current flow to the total magnetomotive force of said machine, thereby to produce flux in said core in accord with the flux of said machine; a movablecoil disposedto be linked with the flux of said core; yielding means restraining motion of said coil; and means for causing current flow through saidcoil in pro portion to the armature current of said machine.

6. A mechanism to measure the torque of a direct current machine of the type having an armature, a shunt field winding, and adifierential compound field winding, said mechanism including a core defining a magnetic fiux path separateand in accord with the relative contributions of shunt field current flow and armature current flow to the total magnetomotive force of said machine, thereby to produce flux in said core in accord with the flux of said machine; a movable coil disposed to be linked with the flux of said core; yielding means restraining motion of said coil; and means-for causing current flow through saidwcoil in proportion to the armature current of said machine 7; A mechanism to measure the torque of a direct current machine of the type having an armature and a field winding and having an effective saturation curve departing substantially from a straight line characteristic, said mechanism including a core defining amagnetic flux path separate from said machine; saidcore having an eITe'ctive saturation curve departing from a straight line characteristic to substantially the same degree as the effective saturation curve of said machine; a winding encircling said fiux path; means to produce an electromotive force across said last winding in accord with the current flow in said field winding; a movable coil disposed to be linked with the flux of said core; yielding means restraining motion of said coil; means for causing current fiowin said coil in accord with the armature current of said machine, the magnetomotive force of said coil being negligible as compared with the magnetomotive force of said last Winding.

8. A mechanism to measure the torque of a direct current machine of the type having an armature and a plurality of field windings and having an effective saturation curve departing substantially from a straight line characteristic, said mechanism including a core defining a magnetic flux path separate from said machine and having an effective saturation curve departing from a straight line characteristic to substantially the same degree as the effective saturation curve of said machine; windings about said core corresponding to said field windings; means to produce electromotive force across each of said last windings in accord with the current flow in the corresponding field winding, said means being proportioned to cause each of said last windings to produce magnetomotive force in said core in accord with the relative contribution of the corresponding winding to the magnetomotive force of said machine, thereby to produce flux in said core in accord with the flux intercepted by the armature. winding of said machine; a movable coil disposed to be linked by the fiux of said core; yielding means restraining motion of said coil; and means for causing current flow through said coil in accord with the armature current of said machine.

9. A mechanism. to measure the torque of a direct current machine of the type having an armature and two field windings and having an efiective saturation curve departing substantially from a straight line characteristic, said mechanism including a core defining a magnetic flux path separate from said machine and having an eiiective saturation curve departing from a straight line characteristic to substantially the same degree as the effective saturation curve of said machine; a pair of windings about said core; means to produce electromotive force across each of said windings in accord with the current flow in the corresponding field winding, said means being proportioned to cause each of said last windings to produce magnetomotive force in said core in accord with the relative contribution of the correspond ing windings to the magnetomotive force of said machine, thereby to produce flux in core in accord with the flux of said machine; a movable coil disposed to be linked with the flux of said core; yielding means restraining motion of said coil; and means for causing current fiow through said coil in accord with the armature current of said machine.

10. A mechanism'to measure the torque of a direct current machine of the type having an armature and a field winding in which the armature exerts substantial magnetomotive force during normal operation and having an effective saturation curve departing substantially from a straight line characteristic, said mechanism including a core defining a magnetic flux path separate from said machine and having an effective saturation curve departing from a straight line characteristic to substantially the same degree as the effective saturation curve of said machine; a pair of windings about said core; means to produce electromotive force across one of said windings in accord with the armature current of said machine and across the other of said windings in accord with the current in the field winding of said machine, said means being proportioned to cause the relative magnetomotive forces of said windings to be in accord with the relative contributions of the field winding of said machine and the armature winding of said machine to the magnetomotive force thereof, thereby to produce flux in said core in accord with the flux of said machine; a movable coil disposed to be linked with the flux of said core; yielding means restraining motion of said coil; and means for causing current fiow through said coil in accord with the armature current of said machine.

11. A mechanism to measure the torque of a direct current machine of the type having an armature, a shunt field winding, and a cumulative compound field winding, and having an effective saturation curve departing substantially from a straight line characteristic, said mechanism including a core defining a magnetic flux path separate from said machine and having an effective saturation curve departing from a straight line characteristic to substantially the same degree as the effective saturation curve of said machine; a pair of windings about said core; means to produce electromotive force across one of said windings in accord with the armature current of said machine and across the other of said windings in accord with the current in the shunt field winding of said machine, said means being proportioned to cause the relative magnetomotive forces of said windings to act cumulatively and in accord with the relative contributions of shunt field current flow and armature current flow to the total magnetomotive force of said machine, thereby to produce flux in said core in accord with the flux of said machine; a movable coil disposed to be linked with the flux of said core; yielding means restraining motion of said coil; and means for causing current flow through said coil in proportion to the armature current of said machine.

12. A mechanism to measure the torque of a direct current machine of the type having an armature, a shunt field winding, and a differential compound field winding, and having an effective saturation curve departing substantially from a straight line characteristic, said mechanism including a core defining a magnetic flux path separate from said machine and having an effective saturation curve departing from a straight line characteristic to substantially the same degree as the effective saturation curve of said machine; a pair of windings wound about said core; means to produce electromotive force across one of said windings in accord with the armature current of said machine and across the other of said windings in accord with the current in the shunt field winding of said machine, said means being proportioned to cause the relative magnetomotive forces of said last windings to act differentially and in accord with the relative contributions of shunt field current flow and armature current flow to the total magnetomotive force of said machine, thereby to produce flux in said core in accord with the flux of said machine; a movable coil disposed to be linked with the fiux of said core; yielding means restraining motion of said coil; and means for causing current fiow through said coil in proportion to the armature current of said machine.

13. A mechanism to measure the torque of a direct current machine of the type having an armature and a field winding and having an effective saturation curve departing substantially from a straight line characteristic, said mechanism including a core defining a magnetic flux path separate from said machine; said core having an effective saturation curve departing from a straight line characteristic to substantially the same degree as the effective saturation curve of said machine; a winding encircling said flux path; a movable coil disposed to be linked with the fiux of said core; and yielding means restraining the motion of said coil.

GEORGE E. FROST.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 452,326 Weston May 12, 1891 698,682 Duncan Apr. 29, 1902 1,841,892 Highfield Jan. 19, 1932 1,942,920 Fawkes Jan. 9, 1934:

2,028,374 Anderson Jan. 21, 1936 2,363,377 Wrathall Nov. 21, 1944 2,385,005 Langer Sept. 18, 1945 FOREIGN PATENTS Number Country Date 282,722 Germany Mar. 17, 1915 

